Field of the Invention
The present invention relates to an apparatus and a method of manufacturing semiconductor device, including the treatment of substrate surface, specifically the treatment of surface of group IV semiconductor.
Related Background Art
Conventionally semiconductor Si substrate is subjected to wet-cleaning. The wet-cleaning has, however, problems of failing to completely remove water-marks in dry state, failing to control etching of very thin oxide film, requiring large apparatus, and the like. Furthermore, when the semiconductor substrate is exposed to atmospheric air for a long time after the wet-cleaning, there arise problems of forming native oxide film on the surface thereof and adsorbing carbon atoms thereon to inhibit film-forming of Si single crystal, generating irregular profile of film, generating impurity level at the interface of gate insulation film, and the like.
Therefore, surface oxide film was removed by applying UHV vacuum heating to 750° C. or higher or by applying heating to 800° C. or higher in an H2 atmosphere before film formation. However, as miniaturization of device progresses and dielectric insulation film/metal electrode is used, the device needs to be manufactured at lower temperatures. Thus the device manufacturing needs to be done at 650° C. or lower temperature. As a result, the wet-cleaning has its limits, and there arises a need of dry-cleaning method which conducts treatment of semiconductor substrate in a vacuum before film-forming. The reverse sputtering method using argon plasma is one example of the method (Japanese Patent Laid-Open No. 10-147877). The disclosed method, however, presumably cuts also the Si—Si bond on the surface of the semiconductor substrate. In that case, problems arise such that oxide film is immediately formed on the Si-absent portion, that contaminants likely adhere to the dangling bond of Si, and that the sputtered oxide and contaminants adhere again to the side wall of the substrate. These problems adversely affect the succeeding step, (such as inhibition of epitaxial growth and formation of highly resistant portion on the silicide interface). Furthermore, damages on the device are also the problem.
Japanese Patent Laid-Open No. 2001-144028 describes that, after removing the silicon oxide film 401 from the surface of the substrate 5 using a plasmatized F2 gas, the hydrogen radicals are irradiated to remove the F component adhered to the surface of the substrate (see FIG. 9A). Japanese Patent Laid-Open No. 04-96226 describes that, after removing the Si native oxide film 401 from the surface of the substrate 5 using F2 gas, the radicalized hydrogen is irradiated to the substrate to terminate the bonding operation by the hydrogen (see FIG. 9A). Japanese Patent Laid-Open No. 06-120181 discloses a technology of terminating the bonding operation by hydrogen on the surface of the substrate 5 using hydrogen ions after removing the oxide film 401 on the substrate surface by HF plasma (see FIG. 9A). Since, however, the plasmatized F2 gas contains not only the radicalized fluorine gas but also the ionized fluorine gas. There arises a problem of generating irregular surface on removing the silicon oxide film from the substrate surface. Furthermore, there is a possibility of removing a portion of the substrate itself not only removing the silicon oxide film thereon. In addition, since the semiconductor substrate is exposed to plasma, Si—Si bond is also cut off. In that case, there arise problems that the oxide film is immediately formed on the Si-absent portion, that the contaminants likely adhere to the dangling bond of Si, and that the sputtered oxide and contaminants adhere again to the side wall of the substrate. These problems adversely affect the succeeding stage, (such as inhibition of epitaxial growth and formation of highly resistant portion on the silicide interface). Furthermore, damages on device are also the problem. According to the disclosure, gas is decomposed positively by plasma to generate hydrogen radicals and hydrogen ions. When fluorine residue on the surface of the substrate is removed by the hydrogen radicals and the hydrogen ions, there arise problems of contamination by metal coming from the chamber, of excess etching because of large etching rate on the base Si, and the like. Furthermore, since HF as the reaction product likely adheres again to the surface of the substrate, sufficient F-removal effect is not attained.
Japanese Patent Laid-Open No. 2001-102311 describes that a cleaning gas such as fluorine is supplied to the plasma-forming part having the plasma-forming chamber which is separated, by a plate having feed holes therethrough, from the film-forming chamber where the substrate is placed, thus generating radicals by generating plasma in the plasma-forming part, and the fluorine radicals are fed to the film-forming space containing the substrate via the feed holes, thereby irradiating the radicals to the substrate for cleaning thereof. Japanese Patent Laid-Open No. 2002-500276 discloses a substrate cleaning method using a plate distributing the gas excited by a remote plasma source, through which plate the radicals are supplied to clean the substrate. Since, however, the surface of the semiconductor substrate cannot be exposed to an atmosphere which suppresses the excitation energy of radicals, etching with high Si selectivity cannot be conducted, which then raises a problem of failing to remove the native oxide film without deteriorating the surface roughness.
Japanese Patent Laid-Open No. 2002-217169 discloses an apparatus for conducting entire cleaning step in a vacuum to remove foreign matter applying simultaneously a physical action of friction stress generated by a high velocity gas flow. According to the disclosure, adsorption of impurities and generation of native oxide during vacuum transfer are suppressed, thus improving the production efficiency. Even if the foreign matter can be removed, however, the native oxide film and the surface roughness remain on the surface at an order of atomic layer thickness. That is, to attain the effect of device characteristic improvement by the continuous transfer in vacuum, there are required the cleaning technology to control the highly selective etching of Si and native oxide film at an order of atomic layer thickness, and the transfer of substrate and the film-forming thereon without exposing the substrate to atmospheric air. That kind of control technology and vacuum operation should provide good device characteristics of low interface state at the joint between semiconductor and dielectric insulation film, and of small fixed charge in the film.
Japanese Patent Laid-Open No. 10-172957 describes that the oxide film was able to be selectively removed by a mixed gas of: argon, helium, xenon, and hydrogen which are excited by a remote plasma source; and HF gas fed in downstream side, and that no damage was observed on the silicon substrate. The removal, however, did not satisfy the flatness required in recent years.
[Patent Document 1] Japanese Patent Laid-Open No. 2001-144028
[Patent Document 2] Japanese Patent Laid-Open No. 04-96226 (1992)
[Patent Document 3] Japanese Patent Laid-Open No. 06-120181 (1994)
[Patent Document 4] Japanese Patent Laid-Open No. 2001-102311
[Patent Document 5] Japanese Patent Application Publication No. 2002-500276